This is a proposal to continue the Early Detection of Liver Cancer Biomarker Discovery Laboratory of the EDRN. Our over-all goal has been to identify and develop biomarkers for the early detection of liver cancer. Our hypothesis, tested within the first period of support, that changes in the amount or modification of serum polypeptides correlate with the onset of hepatocellular carcinoma (HCC) or hepatitis, has been confirmed. We will build upon our exciting initial proteomic studies of cell lines and human serum derived from those at risk for liver cancer in which several promising approaches and biomarker leads were found. For example, we will determine the possibility that GP73, a resident Golgi protein whose level in the circulation was found by us to correlate with a diagnosis of liver cancer, can be used as a biomarker of disease. Pilot studies, in cooperation with NCI consortia, showed that GP73 levels were among the best biomarkers of liver disease to be tested. Moreover, different glycoforms appeared to be associated with tissue and secreted states and may in themselves vary with clinical status. Therefore, the GP73 detection assay, developed by us, will be refined to exploit our new insights to improve specificity, and made robust for larger validation studies to determine true sensitivity, specificity and selectivity, in people. In addition, new biomarkers discovered by our proteomic and glycobiology research will be contributed to the pipeline. The possibility that promising biomarker levels are influenced by antiviral therapy will also be determined. The most promising candidates, chosen on the basis of selectivity and sensitivity criteria, will be advanced to the validation stage for ultimate utility determination.